Implement Model-Driven-Views spec for Dart

sdk/lib/observe/observe.dart

Index: sdk/lib/observe/observe.dart
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+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * *Warning*: this library is experimental, and APIs are subject to change.
+ *
+ * This library is used to observe changes to [Observable] types. It also

[Lasse Reichstein Nielsen, 2013/05/06 10:58:58]

I think the Observable name is too generic.
This is very much a *property-change* observable, and I think it should be part
of the name.

[Jennifer Messerly, 2013/05/07 05:43:38]

It's intended for all observable objects. List and Map usage is not exactly
"property change". What other kinds of observables did you have in mind?

My fear is that "PropertyChangeObservable" is really long and wordy, especially
once it gets mixed in or extended. The JS version is simply "Object.observe".

I moved to package:observe, does that alleviate some of the concern?

We have plenty of time to improve this! :) I would love to get more help :).
Observability is a huge topic; no doubt one could spend a lot of time making it
better and more comprehensive. Reactive programming is hugely beneficial for UI
work, and customers are already using our existing Observable library,
incomplete though it may be.

+ * has helpers to implement [Observable] objects.
+ *
+ * For example:
+ *
+ *     class Monster extends ObservableMixin {

[floitsch, 2013/05/06 17:37:46]

As written in the other file: I don't like to extend a Mixin. It feels wrong.

[Jennifer Messerly, 2013/05/07 05:43:38]

Done.

+ *       int _health = 100;
+ *       static const _HEALTH = 'health';
+ *       get health => _health;
+ *       set health(value) {
+ *         _health = notifyChange(_HEALTH, _health, value);
+ *       }
+ *       void damage(int amount) {
+ *         print('$this takes $amount damage!');
+ *         health -= amount;
+ *       }
+ *       toString() => 'Monster';
+ *
+ *       // These methods are temporary until dart2js supports mirrors.
+ *       getValue(key) {
+ *         if (key == _HEALTH) return health;
+ *         return null;
+ *       }
+ *       setValue(key, val) {
+ *         if (key == _HEALTH) health = val;
+ *       }
+ *     }
+ *
+ *     main() {
+ *       var obj = new Monster();
+ *       obj.changes.listen((records) {
+ *         print('Changes to $obj were: $records');
+ *       });
+ *       // Asynchronously schedules delivery of these changes

[Lasse Reichstein Nielsen, 2013/05/06 10:58:58]

"Schedules asynchronous ..."? 
(Nitpick - the scheduling happens now, the delivery happens asynchronously :).

[Jennifer Messerly, 2013/05/07 05:43:38]

Done.

+ *       obj.damage(10);
+ *       obj.damage(20);
+ *       print('done!');
+ *     }
+ */
+library dart.observe;
+
+import 'dart:async';
+import 'dart:collection';
+import 'dart:math' as math;
+
+part 'list_diff.dart';
+part 'observe_path.dart';
+part 'observable.dart';
+part 'observable_box.dart';
+part 'observable_list.dart';
+part 'observable_map.dart';